When to Plant Potatoes in Washington
Published: April 24, 2026
Washington gardeners in Zone 4b have a 21-week frost-free window for potato (May 7 to October 1). Cool-season crops like potato do well here because the short, cool summers match the plant's temperature preferences naturally. This guide gives exact dates for Washington based on your local frost calendar.
Potato Planting Dates for Washington
| Start seeds indoors | Year-round |
| Last frost (average) | May 7 |
| Direct sow outdoors | April 16–26 |
| Expect first harvest | June 25 – August 14 |
| First fall frost (average) | October 1 |
⚠ Plant seed potatoes 2–4 weeks before last frost when soil is workable and above 45°F. Hill soil up around stems as plants grow. Needs well-drained, loose soil.
Growing Potatoes in Washington's Climate
Washington's cold Zone 4b climate is close to ideal for potato. The cool springs and moderate summers match the plant's natural temperature preferences, producing crisp, sweet, slow-bolting harvests that hot-climate gardeners cannot grow.
The fall potato crop in Washington is often better than the spring crop. Plants mature as temperatures cool in September and October, concentrating sugars and tightening heads or roots. Light frost can improve flavor; hard frost signals harvest time.
Common potato pests to watch for in Washington include Colorado Potato Beetle and Wireworm. The first line of defense is companion planting: Bean and Corn planted nearby discourage several of these pests by confusing host-plant identification or repelling adults before they can lay eggs. Weekly garden walks in the early morning catch problems when they're still manageable.
Potato Garden Calendar for Washington
| Month | Task | Notes |
|---|---|---|
| January | — | Dormant season |
| February | — | Dormant season |
| March | — | Dormant season |
| April | Direct sow seeds | Sow seeds 1/4–1/2 inch deep, 12 inches apart |
| May ← | Watch for bolting | Harvest promptly; spring heat arrives quickly |
| June | First harvest window opens | Potato begins producing 70–120 days after transplant |
| July | — | Dormant season |
| August | — | Dormant season |
| September | — | Dormant season |
| October | First frost approaches | Harvest remaining potato; cover plants on frost nights |
| November | — | Dormant season |
| December | — | Dormant season |
Potato Growing Tips for Washington Gardeners
- •Cut seed potatoes into 2-inch chunks with at least two eyes each, then let cut surfaces heal for 24–48 hours before planting.
- •Plant 4 inches deep and 12 inches apart in loose, well-drained soil; add compost but avoid fresh manure.
- •Washington's short growing season means start seeds indoors under grow lights — don't rely on windowsill light which produces leggy, weak seedlings that struggle outdoors.
- •Cover young transplants with floating row covers for the first 2–3 weeks outside. The 3–5°F of protection reduces frost damage risk and accelerates early growth.
- •Hill up soil around stems when plants reach 6 inches tall to cover developing tubers and prevent green potatoes.
Companion Planting for Potatoes in Washington
In Washington's cold climate, planting potato with Bean and Corn helps deter pests and improve soil. Avoid planting near Tomato and Pepper, which inhibit potato growth through root chemistry or shared pest pressure. See the full potato companion planting guide for the complete list.
Potatoes Planting Dates by City in Washington
Top cities in Washington — select for city-level frost dates and planting calendars.
Frequently Asked Questions
When should I plant potato in Washington?
In Washington (Zone 4b), start potato seeds indoors around Year-round and transplant outdoors around null — 0 weeks after the state's average last frost of May 7.
What is the last frost date in Washington?
Washington's average last frost date is May 7 in the state's most common Zone 4b. Frost dates vary by city — higher elevations and northern counties run 1 to 3 weeks later than the state average. See the city list below for city-level frost dates.
Can I grow potato year-round in Washington?
potato is a cool-season crop in Washington, with spring and fall windows. Summer heat bolts the plants before they can produce a harvestable crop. Succession planting every 2–3 weeks stretches the harvest window.
What potato varieties grow best in Washington?
For Washington's Zone 4b, consult a local nursery or extension office for potatoes variety recommendations.
When do I start potato seeds indoors in Washington?
Potato does not need indoor starting in Washington — direct sow around April 16–26 once soil reaches 45°F. Indoor starting is not recommended for this crop because potato transplants poorly.